Cheesy Potato and Sausage Casserole

I saw this fabulous casserole on Pinterest but when I got a load of the calorie and fat content I decided a makeover was in order. The original called for Velveeta cheese, a big no-no in my book so I swapped that for a low fat homemade cheese sauce with no artificial anything in it. I swapped the full fat pork sausage for low fat smoked chicken sausage.

Serves 8

5 large potatoes, peeled and diced
2 Hillshire Farms smoked chicken sausages, cubed
3 cups 1% milk
3 tablespoons smart balance margarine
1/4 cup flour
salt and pepper
1 tsp dried thyme
3 1/2 cups shredded low fat cheddar cheese
1 onions, minced

Preheat the oven the 350. Spray an oblong baking dish with cooking spray. Boil the potatoes in salted water until just tender. Drain and cool. Melt the margarine in a medium saucepan. Add the onion and cook until translucent, about 5 minutes. Add the flour and stir until well combined. Add the milk slowly to the flour mixture, whisking continuously. Continue to whisk until the flour is combined and there are no lumps. Season with salt and pepper. Switch to a spoon and stir until the mixture begins to boil and has thickened. Turn off the heat and stir in 3 cups of cheese. Whisk until the cheese is combined and melted. Place the potatoes and sausage in the baking dish. Season with salt, pepper and the dried thyme. Pour the cheese sauce over the top and gently stir to combine. Sprinkle the remaining cheese over the top. Cover with foil and bake for 30 minutes. Remove the foil and broil for 3-5 on high until the cheese is browned;. Serve